[117] There was nothing
unusual about the visitor who came to Wright Field on the chilly,
overcast day of 24 March 1954. He was one of dozens who were
processed through the large visitor's center adjoining the security
fence to go to one of the many buildings of the huge Wright Air
Development Center. Typical also was the reason for his visit. He was
bringing an idea, neatly packaged in a brochure, and seeking a
contract. The Center receives hundreds of unsolicited proposals
annually and is geared to evaluate them. As with most such proposals,
this one was destined to be rejected. What was [118] unusual, however,
was the novel solution proposed for a difficult problem, the
sensitive nature of the subject, and the timing. The proposal
triggered waves of interest within the government, and there followed
a series of events involving hydrogen that extend to this day-events
that shuttled the proposer to the sidelines and left him bewildered
and embittered. His name is Randolph Samuel Rae (1914- ).

Randy Rae is a quiet, soft-spoken man with the
imagination and creativeness that mark the practical innovator and
inventor. He received his engineering education at a Swiss technical
school and began his career in electronics and underwater detection
systems for locating submarines. He worked for the British Admiralty
from 1939 to 1948, serving" in four research and development groups
in underwater acoustics, aerodynamics, thermodynamics, and
propulsion, rising to the position of a principal scientific officer.
He came to the United States in 1948 and worked in the Applied
Physics Laboratory of Johns Hopkins University for four years. He
started in aerodynamics and developed a supersonic diffuser for
ramjet engines and later was placed in charge of the development of a
complete guided missile system. More at home with technical details
than overall project management, Rae soon was immersed in a difficult
missile stability and control problem and devised a solution
involving a gyro with a mechanical feedback. The system was put out
for bid and a small company, Summers Gyroscope, won the contract. Rae
met a kindred soul in dynamic, innovative Thomas
Summers.12

The missile development that Rae was managing
used a ramjet engine for propulsion. A ramjet operates at high
altitudes and speeds, but as with all air-breathing engines, it is
altitude-limited. The ramjet's altitude-speed limitations set Rae to
thinking about other solutions to the problem in April 1953. Was
there a way to operate at very high altitudes but at lower speeds,
specifically in the subsonic speed range? The rocket was not the
answer, for although it operates independent of the atmosphere, it is
very inefficient at low speeds. Could he combine the
altitudeindependent feature of the rocket engine with a propulsion
system efficient at low speeds? The most efficient means for aircraft
propulsion at low speeds is the propeller, but it is, of course,
altitude-limited. Rae conceived of using a rocket as a gas generator
to drive a turbine which, through suitable gearing, would drive a
large propeller. Such a propulsion system had no place in the
high-speed, high-altitude operating regime of the Navy's work at the
Applied Physics Laboratory. Rae became so intrigued with his concept
that he left APL/JHU to work full-time on the new propulsion system.
He soon learned the handicaps a lone inventor faces. He needed not
only monetary support but a corporate identity as well. He turned to
his friend, Thomas Summers, who very generously offered both,
although propulsion was a far cry from gyroscopes and
instruments.

Rae joined Summers in September
1953and
began analysis of what he called the Rex engine. The week before
Christmas, Summers engaged Homer J. Wood, a mechanical engineering
consultant. Wood had left the Garrett Corporation, makers of small
gas turbine engines and other aircraft components, in October after
ten years service during which he became assistant chief engineer in
charge of turbomachinery. Wood assisted in the analysis and design of
Rae's new engine.13

By March 1954, Rae was ready to present his
idea to the government. He visited the headquarters of the Air Force
Air Research and Development Command (ARDC),
[119] then located in Baltimore, and discussed his idea
with Col. Donald Heaton, chief of the aeronautics and propulsion
division, and Lt. Col. Langdon F. Ayers, who headed the propulsion
branch. The two were engaged in planning research and development to
increase the altitude capability of aircraft. and Rae's idea caught
their interest. They suggested that he visit Wright Field and discuss
the proposal with the specialists there.14 This was what brought Rae to Wright Field on 24 March
1954, with brochures describing the proposal.

Rae presented his proposal to a group in the
new developments office ofWADC and passed out copies of his brochure.
It bore the date of February 1954 and the title, "REX-1, A New
Aircraft System" (fig.
27). Rae described it as "a lightly
loaded low speed plane having an exceptional L/ D (lift/ drag)
characteristic." By lightly, loaded, he meant a low weight per unit
area of wing; the aircraft resembled a low-powered glider. The speed
of about 800 kilometers per hour would make a military airplane quite
vulnerable were it not for the very high operational altitude that
Rae proposedover 24 000 meters, which was well above the capability
of other aircraft and hopefully beyond the range of antiaircraft
weapons. What stirred the interest of the Wright Field audience was
the novel engine that Rae proposed: a three-stage turbine engine
using liquid hydrogen and liquid oxygen (fig. 28).
Ahead of each turbine was a small combustion chamber. All of the
hydrogen and part ofthe oxygen were fed to the first combustion chamber.
This partial combustion of the hydrogen produced a gas temperature of
about 1100 K, the then practical limit for turbine materials.
After....

[120] Fig. 28. Schematic
of Rex I engine. Liquid hydrogen and oxygen, gasified by passing
through heat exchangers, flow to three small combustion chambers. The
hot gases drive three turbines connected to a common shaft. The gases
for the second and third turbines are a mixture ofthe exhaust from
the previous turbine and combustion gases. After the third turbine,
the exhaust gases supply heat for the heat exchangers and then
discharge. From the brochure "REX-1, A New Aircraft System," by R. S.
Rae, Summers Gyroscope Co., Feb. 1954.

....leaving the first turbine, the gases were
reheated by adding additional oxygen and burning. The process was
repeated for the third turbine. After leaving the thir d turbine, the
gases passed through heat exchangers to heat the incoming liquid
hydrogen and liquid oxygen.* Rae was attracted to hydrogen by its high specific
heat, relatively low combustion temperature, and high energy content.
15

The three high-speed turbines, on a single
shaft, were geared down to drive a propeller. The conceptual engine
was very compact (fig.
29). With both liquid hydrogen and
liquid oxygen on board the aircraft, the turbine engine was
independent of altitude. Rae proposed to use the turbine engine to
drive a large propeller which provided the propulsive thrust by
accelerating atmospheric air. The propeller, obviously, depended very
much on altitude; the size of the propeller needed for thrust at high
altitude later became an issue in evaluating the proposal. After
pointing out the military advantages of a high-altitude aircraft, the
brochure ended with a low-keyed request: "The Summers Gryoscope
Company is desirous of obtaining a Government contract to develop the
revolutionary REX-I aircraft system."

As is usual in such cases, Rae left that day
wondering how his proposal would be received, after the noncommittal
attitude of the Wright Field listeners. In fact, his proposal caught
the attention and interest of many in the Air Force and
several....

[121] Fig. 29. Drawing of
Rex I engine showing the heat exchanger, hydrogen-oxygen combustors,
and three turbines. In the foreground is a reduction gear train
transmitting power from the high-speed turbines to the engine
application which, in the first proposal, was a propeller. From the
brochure "REX-1, A New Aircraft System," by R. S. Rae, Summers
Gyroscope Co., Feb. 1954.

...analyses were started immediately. In
response to a request for more information, Rae sent considerable
detail about the proposed engine with a cost analysis. The cost was
estimated to be on the order of $3 million a year for three
years.16

In an analysis completed in May, Weldon Worth,
R.E. Roy, and R.P. Carmichael examined propulsion aspects of the
proposal and concluded: "There are numerous examples of optimism in
the proposal but nevertheless, if the development does not bog down
under adverse problems that result from impractical features, the
small engine size and weight, the reasonably low fuel consumption,
the high altitude combustion capability of hydrogen, and the
surprising aircraft performance present a stimulating approach to a
high attitude performance regime well beyond present aircraft
capabilities." They added that there were other possible ways of
achieving the same flight regime and discussed adverse technical
factors that were based on hydrogen's characteristics and the
possibility, from preliminary estimates of the propeller laboratory,
that a much larger propeller than proposed might be necessary. Large,
insulated lightweight tanks and a circulating gas-heat exchanger
system were considered major development problems; these and a larger
propeller or fan could substantially increase rize and mass of
tankage, engine, and gearing between engine and
propeller.17

In Rae's opinion, Wright Field's principal
objections to his proposal centered on mass estimates and propeller
size. He was kidded that his airplane would need a runway with
trenches ori each side of the wheels to accommodate propellers 12
meters in diameter. Rae believes he was vindicated later on both
these points, but at the time he felt that the brickbats were coming
at him thick and fast.18

* Rae used an initial pressure of 69.7 atm, and a heat
exchanger efficiency of 90%. He quoted an aachievable specific fuel
consumption of 1 lb/hp (0.61 kg/kW .
hr) and gave data indicating this
could be attained with a four-stage turbine system with a turbine
efficiency of 50%. He had analyzed both three-and-four-stage
turbines; by specific fuel consumption, he apparently meant both
hydrogen and oxygen.